• To identify contact allergens with patch testing in patients with chronic idiopathic urticaria living in the New England area. [ Time Frame: Late read: three days after allergens for patch testing are placed ] [ Designated as safety issue: No ]
  

• To determine if avoidance of contact allergens causes the resolution of chronic urticaria in those patients with positive patch test results. [ Time Frame: 1-3 months after patch testing performed. ] [ Designated as safety issue: No ]
  

Study Visits: Patients will be seen on Day #0, which will be a Monday, and the study will be explained. If they agree to participate, consent will be signed and they will be interviewed to determine any relevant occupational or personal exposures to potential allergens. They will be examined to determine if they have sufficient normal skin to undergo patch testing. Patients will be allowed to use antihistamines to treat pruritus as antihistamines do not abrogate T-cell-mediated immune reactions.

Scanpor (paper) tape strips of 10 allergens each contained within 10-mm Finn (aluminum) chambers will be applied to the patient's back. All patients will be tested to the Tufts Medical Center standard series, fragrance, cosmetics/preservative, and textile series. Based on patient history, other appropriate allergen series will be added.

After two days (on Day #2, a Wednesday), patches will be removed and the areas will be inspected for type IV hypersensitivity reactions including papules, edema or vesicles. The testing areas will be marked using a surgical marker and the patients will return the following day (on Day #3, a Thursday) for a delayed reading.

Interpretation: Patch test reactions will be interpreted by using NACDG criteria: negative reaction (macular erythema); 1+ (weak reaction; non-vesicular erythema, infiltration, and possibly papules); 2+ (strong reaction; edematous or vesicular); 3+ (extreme reaction; spreading, bullous, or ulcerative lesions), or irritant reaction. If contact allergens are found, patients will be educated about allergen avoidance and given listings from the Contact Allergen Replacement Database delineating products they may use which do not contain their allergens.

Follow-up Interview: One to three months after patch testing, the patients will be contacted to determine whether allergen avoidance has resulted in any improvement in their chronic urticaria. They will be asked how well they have adhered to allergen avoidance (completely avoided, mostly avoided, somewhat avoided, or not at all avoided) and how their urticaria has been since changing their habits (a response score: completely resolved, mostly improved, somewhat improved, no change, or worse).

Costs: there will be no costs to the patients to participate in this study. Patients will be seen as regular patients at Tufts Medical Center, and their insurance providers will be billed for the visits. A stipend will be provided to patients to cover the costs of their transportation.